This proposal requests a matrix-assisted laser desorption/ionization and electrospray ionization quadrupole/orthogonal time-of-flight mass spectrometer (MALDI/ESI-Q-TOF-MS) to bring our Proteomics/Mass Spectrometry Laboratory's capabilities up to the state-of-the-art and to increase our ability to meet the ever increasing volume and intensity of work by our investigators. This request is essential to support our ongoing research programs and to stimulate and enable new collaborative research initiatives on protein identification, posttranslational modification characterization, gene discovery, and functional proteomics. Currently, there is no MALDI/ESI-Q-TOF mass spectrometer at the Mount Sinai School of Medicine, which provides a fundamental reason for this request. The MALDI/ESI-Q-TOF mass spectrometer is requested in conjunction with our recent recruitment of Dr. Rong Wang to head the "Proteomics/Mass Spectrometry Laboratory" at the Mount Sinai School of Medicine. Dr. Wang trained at the Johns Hopkins School of Medicine with Dr. Robert J. Cotter and at the Rockefeller University with Dr. Brian T. Chait, two of the world's premier mass spectrometrists. He has years of experience working in biomedical mass spectrometry and published more than 40 articles on the development of mass spectrometry methodology and its application to a wide range of biological problems. The purchase of the MALDI/ESI-Q-TOF mass spectrometer is fundamental to the continuing expansion and enhancement of the proteomics research program for human disease and basic research programs on the Mount Sinai campus. As described in this application, over 19 NIH-funded investigators from 7 different departments have specific needs for this mass spectrometer, which will be a shared research resource. Indeed, due to the lack of a more sensitive and high throughput MALDI/ESI-Q-TOF mass spectrometer on campus and the current usage saturation of the other instruments in New York, some of these research projects are seriously delayed or compromised. Thus, the purchase of the MALDI/ESI-Q-TOF mass spectrometer, in conjunction with the recruitment of Dr. Wang, will have a major impact on research capabilities at our institution.